Year	Number of
1990	31.47
1991	32.69
1992	34.06
1993	35.63
1994	37.37
1995	39.3
1996	42.24
1997	45.57
1998	49.27
1999	53.11
2000	57.04
2001	61.31
2002	65.6
2003	70.09
2004	75.02
2005	80.58
2006	84.96
2007	89.78
2008	95.18
2009	101.04
2010	107.38
2011	114.74
2012	122.83
2013	131.76
2014	141.44
2015	151.89
2016	163.25